1. Field of the Invention
The present invention relates to an imaging device and an image display method capable of performing live view display of an image on an electronic view finder.
2. Description Related to the Prior Art
Imaging devices such as digital cameras and digital video cameras, which obtain an image of a subject by causing an image sensor to capture the image of the subject formed by an image capture lens, have come into widespread use. Further, camera modules having an image capture lens and an image sensor are generally mounted on electronic devices such as smartphones, mobile phones, PDAs, and tablet terminals. Accordingly, the camera modules also function as imaging devices. In order to determine a photography area (composition) or perform a focusing operation, generally a view finder is provided in such various imaging devices.
As the view finder, an optical finder that has a finder optical system or an electronic view finder (EVF) that displays an electronic image has been known. The electronic view finder includes a display section that is constituted of a liquid crystal display device and the like, and causes the display section to sequentially display live view images which are captured at a predetermined frame rate and are generated on the basis of imaging signals sent from the image sensor.
Since the imaging device is driven by electric power supplied from a built-in battery, it is preferable to reduce power consumption of the electronic view finder which performs live view display. Hence, there is a known imaging device that detects brightness of the surrounding environment through the illuminance detection sensor and performs power saving driving of the electronic view finder by adjusting a display luminance of an the electronic view finder in accordance with brightness of the detected surrounding environment (JP2009-171167A) Specifically, the imaging device of JP2009-171167A decreases the luminance of the electronic view finder when a surrounding environment is bright, and increases the luminance of the electronic view finder when a surrounding environment is dark.
Although not related to the imaging device having the electronic view finder mounted thereon, there is also a known display device capable of achieving reduction in power consumption by detecting brightness (distinction between day and night) of environment through an illuminance detection sensor and adjusting a luminance and a gray scale of display in accordance with brightness of the detected surrounding environment (JP2009-054534A). A technology disclosed in JP2009-054534A is the same as that in JP2009-171167A in that the display luminance is increased when surrounding environment is bright and the display luminance is decreased when surrounding environment is dark. However, the technology is different in that visibility is prevented from being deteriorated by suppressing the display luminance. The display luminance is suppressed in a way of controlling the gray scale of the display in conjunction with the display luminance. Specifically, particularly in a power saving mode for night scenes when the surrounding environment is dark, the gray scale of the display is increased more than a power saving mode for day scenes. Thereby, visibility is secured while the luminance is suppressed.
So far as the imaging device is driven by a battery, it is important to suppress power consumption of respective sections such as the electronic view finder, but the power consumption of a recent display device is suppressed using LEDs as a light source, as compared with the display device used in the past. Further, a capacity of the battery also has increased. Hence, the importance of suppressing power consumption of the electronic view finder has relatively decreased, and thus a recent imaging device is able to perform live view display at a substantially arbitrary brightness.
Recently, in the electronic view finder, there has been a demand for improvement in performance for performing photography comfortably such as an improvement in visibility. For example, when the display luminance of the electronic view finder is excessively brighter than a subject or surrounding environment, this may blind a user's eyes, may give a feeling of fatigue, and so on, that is, this prevents photography from being performed comfortably. Consequently, although power consumption is not intended to be suppressed, as described in JP2009-171167A and JP2009-054534A, it is preferable that the brightness of the surrounding environment is detected and the display luminance of the electronic view finder is controlled.
However, in such a case where a night scene is photographed, specifically, in a case where a subject or surrounding environment is dark and the display luminance of the electronic view finder is set to be low, even when the display luminance is intended to be matched with the brightness of the detected subject or the brightness of the detected surrounding environment, the display luminance may actually deviate from a desired display luminance. One reason for this is that, near the lower limit of a driving voltage of the electronic view finder, individual differences of variations in input/output characteristics and temperature dependent characteristics are large due to manufacturing errors and the like.
The blinding of a user's eyes and the feeling of fatigue, which are caused by excessively bright display of the electronic view finder, are remarkable when a subject or surrounding environment is dark. Hence, in such a case, it is necessary to reliably adjust the display luminance in accordance with the subject or the surrounding environment.